Know Your Larvae

Everyone knows that a butterfly was once a caterpillar. But what was a ladybug before it was...well, a ladybug? It was a larva, of course—just as that butterfly was. Both of these insects (and more than a million others) are arthropods, a group of animals that have hard external skeletons, segmented bodies, and jointed appendages. Their exoskeletons prevent the manner of growth those of us with internal skeletons experience; in order for insects to grow into sexually mature adults, they need to complete several life stages, a process called metamorphosis. Those that undergo simple metamorphosis start out as nymphs that appear similar to adults, except they are smaller, often have different coloration, and may lack wings. Think grasshoppers and squash bugs: If you've seen the adult insect, you'll also recognize the young. Insects that undergo a complete metamorphosis, on the other hand, are a greater challenge for gardeners to know, because their young, called larvae, look nothing like the adult forms. Consider the Japanese beetle grub, a housefly maggot, or a gypsy moth caterpillar: All change dramatically in appearance when they become adults.

Learning to recognize insects in their larval form can be a big boon to gardeners. It may mean the difference between introducing appropriate pest control and accidentally wiping out a population of beneficial insects. Here are a few common examples of larval insects to get you started.

Keep reading to learn your larvae. (Be sure to mouse over the images to see the adult insect)

Good Bug: Ladybug

Larval ladybugs look a bit like miniature alligators with three pairs of legs behind the head and an elongated, tapered abdomen. Most of the 200-some North American species are black with red, orange, or yellow markings. They actively move about plants, consuming hundreds of small pests and insect eggs per day.

Good Bug: Green Lacewing

The larvae of these beneficial insects are also called "aphid lions" due to their voracious appetite for aphids, lace bugs, small caterpillars, and many other insects. They are similar in shape to ladybug larvae but are light brown and have a pair of large, curved mandibles for capturing their prey.

Good Bug: Syrphid Flies

Because this beneficial is a fly, its larvae are called maggots. The non-stinging adult flies look much like bees with their yellow-and black markings. They feed on nectar and pollen, while the larvae are active insect predators. Larvae—small, pale, wormlike maggots—crawl among populations of pest insects and consume them as they go.

Bad Bug: Sawflies

There are many species of sawflies, all with larvae that resemble caterpillars (although they are anatomically different). The larvae ingest a variety of plant leaves and conifer needles. Several species of sawflies are gregarious, so it isn't uncommon to find large groups of them feeding together on a plant. Others, such as columbine, rose, hollyhock, and hibiscus sawflies, feed solo, skeletonizing leaves as they feed.

Bad Bug: Colorado Potato Beetle

Larvae and adults of this pest graze on potato plants, quickly defoliating them. The larvae are reddish orange grubs with black heads and several black dots along their sides. They have three pairs of legs in front of their rounded abdomens.

Bad Bug: Asparagus Beetle

Adult beetles feed on emerging asparagus spears, while the larvae chomp on the ferns, causing dead spots and decreased plant vigor. The grublike larvae are army green with small black heads and measure up to 1/4 inch in length.